Noncontact localized electrochemical deposition of metal thin films

ABSTRACT

A method of selectively electroplating metal features on a semiconductor substrate having a conductive surface. An electrode assembly that includes a plurality of adjacent, mutually spaced and electrically isolated electrodes connected in series so as to be oppositely polarized when a voltage is applied thereacross is positioned over the substrate and an electrolyte solution is applied to the conductive surface. The electrode assembly and the conductive surface may be positioned in close proximity to, but without contacting, one another. A voltage is applied to the electrode assembly, which causes a metal film to selectively form on portions of the conductive surface that are positioned beneath an electrode exhibiting a positive polarity and, thus, negatively charged. Portions of the conductive surface positioned beneath electrodes exhibiting a negative polarity remain unplated. A DC power supply may be employed, the electrode polarity in such case being fixed or, alternatively, an AC power supply may be employed so as to cyclically vary electrode polarity and cause metal deposition beneath each electrode. An electroplating system is also disclosed.

FIELD OF THE INVENTION

The present invention relates to electrochemical deposition of a metalfilm. More specifically, the present invention relates to a noncontactmethod of selectively electrochemically depositing metal features of adesired size and shape and at desired locations on a surface of asubstrate, such as a semiconductor substrate.

BACKGROUND OF THE INVENTION

To fabricate integrated circuits, multiple conductive layers are formedon semiconductor substrates to provide electrical contact betweenconductive components on the semiconductor devices. Since the dimensionsof semiconductor devices have dropped below one micron design rules, theconductive layers are used to accommodate higher densities. Theconductive layers are typically metal layers or metal features that areformed by chemical vapor deposition (“CVD”), physical vapor deposition(“PVD”), atomic layer deposition (“ALD”), or other electrodepositiontechniques, such as electroplating or electroless deposition. Toelectroplate the metal feature, a seed layer is formed on a surface ofthe semiconductor substrate. The semiconductor substrate is directlyattached to a positive electrode and a negative electrode. The surfaceof the semiconductor substrate is then plated with a desired metal byapplying a voltage through the electrodes while an electrolyte solutioncontaining the metal to be plated is flowed over the semiconductorsubstrate. The metal is electroplated onto the entire surface of thesemiconductor substrate.

Electroplating is commonly used to form interconnect lines and vias inmultilayer metal structures in a damascene process. Electroplating theinterconnect lines and vias is one of many steps in fabricating theintegrated circuits. In the damascene process, trenches are formed inthe semiconductor substrate and are filled with a metal, such as copper,aluminum, or tungsten. After the metal is plated, the semiconductorsubstrate is polished, leaving the metal interconnect in the trenchareas. One disadvantage with the damascene process is that since theentire surface of the semiconductor wafer is covered with the metal,undesired portions of the metal must be removed by polishing. A seconddisadvantage is that the metal is deposited nonuniformly on thesemiconductor substrate because the electrodes are connected to edges ofthe semiconductor wafer, which causes a drop in potential towards thecenter of the semiconductor wafer.

Bipolar electrochemical processes have also been developed in which thedesired metal is deposited on the semiconductor substrate withoutcontact between the electrodes and the semiconductor substrate. Forinstance, U.S. Pat. No. 6,120,669 to Bradley discloses a bipolarelectrochemical process that is used to toposelectively deposit a metal,such as a metal wire, between two metal particles. In addition, a methodof plating metal interconnections on a semiconductor wafer using abipolar electrode assembly is disclosed in U.S. Pat. No. 6,132,586 toAdams et al. A metallized surface of the semiconductor wafer ispositioned opposite an anode and cathode of the bipolar electrodeassembly. An electroplating solution of a metal to be plated is thenflowed between the anode and a cathode and the metallized surface of thesemiconductor wafer. A voltage is applied between the electrodes toplate the metal on the metallized surface of the semiconductor wafer.Relative motion is also provided between the bipolar electrode assemblyand the semiconductor wafer while the voltage is applied. By moving thebipolar electrode assembly over the surface of the semiconductor wafer,electroplating of the metal is localized to a small area on thesemiconductor wafer surface and provides more uniform deposits. Thebipolar electrode assembly also enables one side of the semiconductorwafer to be simultaneously plated and deplated (electropolished). Byapplying a positive potential through the anode and a negative potentialthrough the cathode, an area under the anode is electroplated while thearea under the cathode is deplated.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a method of selectively electroplatingmetal features on a semiconductor substrate. Exemplary metal featuresmay include bond pads, redistribution layers or other traces, damascenestructures and interconnects for same, and other conventional metalfeatures found in semiconductor devices, which are formed presently byother techniques. The method comprises providing an electrode assemblythat includes a plurality of adjacent, mutually spaced and electricallyisolated electrodes connected in series so as to be oppositely polarizedwhen a voltage is applied thereacross. As used herein, the terms“positive” and “negative” are respectively used to identify individualelectrodes exhibiting that given polarity at a particular time. Aninsulating material may also be interposed between each of the pluralityof electrodes. The electrode assembly is positioned over a conductivesurface of a substrate and an electrolyte solution is applied to thesubstrate surface. The electrode assembly and the substrate surface maybe positioned in close proximity to one another with the plurality ofelectrodes to be of positive polarity positioned over, but not incontact with, the surface at locations where the metal features are tobe formed. A DC voltage may be applied to the electrode assembly, whichmay generate a fringe electric field that passes through the conductivesurface of the substrate between adjacent positive and negativeelectrodes of the plurality. The fringe electric field may causenegatively charged cathodic portions to form on the substrate surfacebeneath the plurality of positive electrodes and positively chargedanodic portions to form on the conductive surface of the substratebeneath the plurality of negative electrodes. A metal film is depositedfrom the electrolyte solution on the negatively charged cathodicportions of the conductive surface of the substrate that are positionedbeneath the plurality of positive electrodes in a configurationcorresponding to that of the positive electrodes, while portions of thesubstrate surface that are positioned beneath the plurality of negativeelectrodes may remain unplated. Instead of a DC voltage, an AC voltagemay also be applied to the electrode assembly, thus varying the polarityof each electrode with each voltage cycle and reversal of polarity, bywhich metal features may be deposited beneath each electrode as it iscaused to exhibit a positive polarity. The metal film may comprise anyof nickel, copper, cobalt, platinum, aluminum, silver, gold, chromium,iron, zinc, cadmium, palladium, platinum, tin, and bismuth.

The present invention also relates to an electroplating system thatcomprises a plurality of adjacent, electrically isolated electrodesconnected in a series so as to be oppositely polarized when a voltage isapplied thereacross. A power supply is placed in communication with theplurality of electrodes, which may be insulated from each other by aninterposed insulating material, such as an epoxy. The plurality ofelectrodes may, in combination, be configured to produce a fringeelectric field when a voltage is applied thereto by connecting theplurality of electrodes to the power supply in an alternating polaritypattern. The power supply may be an AC power supply or a DC powersupply. As noted above, if an AC power supply is used and an AC voltageis applied to the electrodes of the assembly, each electrode isalternately of positive and negative polarity, enabling metal depositionbeneath each electrode.

The electroplating system may also include a chuck or platen on which asubstrate having a conductive surface upon which metal features are tobe selectively plated is supported. The electrode assembly is supportedusing an electrode support over the chuck or platen in selectedalignment in the horizontal (X-Y) plane and rotationally about avertical (Z) axis perpendicular thereto with the substrate and, morespecifically, with semiconductor die locations thereon. The conductivesurface of the substrate may be positioned in close proximity to theelectrode assembly, such as from approximately 0.1 mm to approximately 1cm away from the electrode assembly and aligned therewith to cause thepattern of plated metal features to be precisely located and configured.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming that which is regarded as the present invention,the advantages of this invention may be more readily ascertained fromthe following description of the invention when read in conjunction withthe accompanying drawings in which:

FIG. 1 is a schematic illustration of an embodiment of an electrodeassembly connected to a power supply;

FIGS. 2-4 schematically illustrate a noncontact method of forming ametal film on a conductive surface of a substrate according to thepresent invention;

FIG. 5 shows a top elevational view of an additional pattern of thepositive electrodes and the negative electrodes in the electrodeassembly;

FIGS. 6 and 7 show side views of a pattern of the positive electrodesand the negative electrodes that is used to form bond pads on theconductive surface of the substrate; and

FIG. 8 is a top elevational view of a pattern of the positive electrodesand the negative electrodes that is used to form bond pads on theconductive surface of the substrate.

DETAILED DESCRIPTION OF THE INVENTION

A metal film is deposited on a conductive surface of a substrate withoutelectrical contact between the conductive surface and electrodes of anelectrode assembly. As such, the metal film is selectively deposited onthe conductive surface of the substrate in the form of discrete metalfeatures by noncontact electrochemical deposition. The metal featuresmay be deposited on the conductive surface of the substrate when afringe electric field, which is generated by applying a voltage across aplurality of positive electrodes and negative electrodes that areconnected in series, passes through the conductive surface of thesubstrate. Conductive polymers or conductive salts may also be depositedon the conductive surface of the substrate rather than the metal film.As shown in FIG. 1, the positive electrodes 2 and the negativeelectrodes 4 are adjacent to one another and are separated by aninterposed insulating material 6. The dimensions of the positiveelectrodes 2, the negative electrodes 4, and the insulating material 6are exaggerated for clarity. In addition, only one positive electrode 2,one insulating material 6, and one negative electrode 4 are labeled inFIG. 1 for the sake of clarity. However, it is understood that thepositive electrodes 2 and the negative electrodes 4 alternate, with theinsulating material 6 separating them. The positive electrodes 2, thenegative electrodes 4, and the insulating material 6 form an electrodeassembly 8. Since the positive electrodes 2 and negative electrodes 4are connected in series and are alternated in position, they provide analternating polarity when the voltage is applied, which, in turn,creates the fringe electric field. As described in detail below, whenthe voltage is applied, a pattern of the metal film deposited onconductive, negatively charged cathodic portions of the substratesurface corresponds to a pattern of metal features located, sized andconfigured in correspondence to the location, size and shape of thepositive electrodes 2 to selectively form metal features on thesubstrate. As noted above and described further below, the polarity ofpositive electrodes 2 and negative electrodes 4 may alternate cyclicallyif an AC power supply is employed to supply a voltage to electrodeassembly 8. However, for simplicity in the initial description of theinvention, electrode polarity is described in a fixed manner with theunderstanding that a DC power supply is employed.

The substrate may be a semiconductor substrate having at least oneconductive surface. The semiconductor substrate may be a semiconductorwafer or other bulk substrate that includes a layer of semiconductormaterial thereon. The term “bulk substrate” as used herein includes notonly silicon wafers, but also silicon on insulator (“SOI”) substrates,silicon on sapphire (“SOS”) substrates, epitaxial layers of silicon on abase semiconductor foundation, and other semiconductor materials, suchas silicon-germanium, germanium, ruby, quartz, sapphire, galliumarsenide, and indium phosphide. The conductive surface of thesemiconductor substrate may be a seed layer, such as a metal or aconductive metal oxide layer. The seed layer may be a thin layer of themetal that is ultimately to be plated or may be formed from a differentmetal. The seed layer may be blanket deposited on the semiconductorsubstrate by conventional techniques, such as by CVD, PVD, ALD, orelectroless deposition.

The positive electrodes 2 and the negative electrodes 4 may be formedfrom an inert, electrical conductive material, such as carbon (graphiteor high purity graphite) or a metal inert to the electrochemistry usedin the process, such as gold, platinum, or another noble metal. As knownin the art, positive electrodes 2 and negative electrodes 4 may beformed in different sizes and shapes and with varying spacingtherebetween. Since the pattern of the metal film that is ultimately tobe deposited on the conductive surface of the substrate depends on thepattern of the electrodes in the electrode assembly 8, the sizes and theshapes of the positive electrodes 2 may be selected based on the desiredpattern of the metal film. Each of the positive electrodes 2 may be adifferent size or shape or the same size or shape, and the negativeelectrodes 4 may be cooperatively sized and shaped to providesubstantially constant lateral spacing between positive and negativeelectrodes for substantially uniform fringe electric field intensity.

To prevent shorting between adjacent, oppositely charged electrodes, theinsulating material 6 may be a dielectric material that isconventionally used in semiconductor devices, such asborophosphosilicate glass (“BPSG”). The insulating material 6 may alsobe a synthetic polymer, such as a polyimide, polyketone,polyetherketone, polysulfone, polycarbonate, polystyrene, nylon,polyvinylchloride, polypropylene, polyetherketone, polyethersulfone,polyethylene terephthalate, fluoroethylene propylene copolymer,cellulose, triacetate, silicone, or rubber. A thin layer of theinsulating material 6 may be used to separate the positive electrodes 2and the negative electrodes 4, the desirable thickness depending uponspacing or pitch between the electrodes and the dielectric constant. Forthe sake of example only, the insulating material 6 may be a dielectricepoxy that is applied to a pattern of positive electrodes 2 and thenegative electrodes 4, such as by dipping the electrode pattern in theepoxy and etching back the epoxy to expose the electrodes.Alternatively, positive electrodes 2 and negative electrodes 4 may beformed by selectively masking and etching a metal layer on a surface ofa dielectric substrate such as, for example, a polyimide or a glass.

The positive electrodes 2 and the negative electrodes 4 may be connectedin series to form the desired pattern of the electrode assembly 8. Aspreviously mentioned, this pattern determines the pattern of the metalfilm that is ultimately to be deposited on the conductive surface of asubstrate 14. For instance, the positive electrodes 2 and the negativeelectrodes 4 may be configured as a pattern of straight, alternatingbars, as shown in FIGS. 2-4, to produce a corresponding or identicalpattern of “stripes” of metal film 26 on the conductive surface ofsubstrate 14. However, additional patterns of the positive electrodes 2and the negative electrodes 4 may be contemplated to form other patternsof the metal film 26 on the conductive surface of substrate 14. Thedimensions and spacing between each of the adjacent positive electrodes2 and the negative electrodes 4 may be adjusted based on the desiredpattern of the metal film that is ultimately to be deposited on theconductive surface of substrate 14.

FIG. 5 illustrates an example of an additional pattern in which thepositive electrodes 2 and the negative electrodes 4 may be connected.The insulating material 6 may separate the positive electrodes 2 fromthe negative electrodes 4. The positive electrodes 2 may form aconductive trace shape 28 that corresponds to a metal feature in theform of a conductive trace to be formed on the conductive surface of thesubstrate 14.

FIGS. 6-8 show additional examples of patterns in which the positiveelectrodes 2 and the negative electrodes 4 may be connected to form bondpads on the conductive surface of the substrate 14. The positiveelectrodes 2 and the negative electrodes 4 may be formed on a surface ofa dielectric layer 30, such as a layer of Krylon® or Kapton®. As shownin FIGS. 6 and 8, the positive electrodes 2 and negative electrodes 4may be formed as by selective etching of a conductive layer laminated toa surface of the dielectric layer 30. The positive electrodes areconnected to the voltage source by a wiring line extending overdielectric layer 30, while surrounding negative electrode 4 may bemerely connected at the edge thereof. The positive electrodes 2 and thenegative electrodes 4 may be separated from one another by material ofthe dielectric layer 30 (see FIG. 7), by an air space 32 (see FIG. 6),or by a combination thereof.

An electroplating system is also disclosed (see FIG. 1). Theelectroplating system may include the electrode assembly 8 and a powersupply 10 selectively operably coupled to the electrode assembly. Thepositive electrodes 2 and the negative electrodes 4 of electrodeassembly 8 may be connected to the power supply 10 through power lines12. The power supply 10 provides the operating voltage and current tothe electrode assembly 8 so that the positive electrodes 2 have apositive potential relative to the negative electrodes 4. The powersupply 10 may be a conventional AC power supply or a conventional DCpower supply that supplies a voltage ranging from approximately 0.1volts to approximately 150 volts to the electrode assembly 8. Forinstance, the voltage supplied to the electrode assembly 8 may rangefrom approximately 0.1 volts to approximately 10 volts. FIG. 1illustrates a DC connection in which a conventional DC power supply isconnected to the electrode assembly 8. It should be noted that in theinstance where an AC power supply is employed, the designation of anelectrode as a positive or a negative electrode will vary with eachpolarity reversal of the cycling power supply.

The conductive surface of substrate 14 may be positioned in closeproximity to the electrode assembly 8, as shown in FIG. 2. While FIG. 2shows the electrode assembly 8 positioned over the conductive surface ofsubstrate 14, additional configurations may be contemplated as long asthe electrode assembly 8 and the conductive surface of substrate 14 arein close proximity. The substrate 14 may be supported on a holdingmechanism, such as a chuck or platen 20, with its conductive surfacefacing upwardly. A temperature at which the substrate 14 is maintainedmay depend on the metal of the metal film that is to be deposited on thesubstrate 14. For the sake of example only, the substrate 14 may bemaintained at a temperature of approximately 25° C. For the sake ofclarity and convenience, the power supply 10 and the power lines 12 arenot shown in FIG. 2. The electrode assembly 8 may be positioned over theconductive surface of substrate 14 through electrode support 16, whichmay include alignment features for cooperative engagement with alignmentfeatures on chuck or platen 20 to provide precise alignment in the X-Y(horizontal) plane and precise rotational alignment about the Z(vertical axis) perpendicular to the X-Y plane with respect to substrate14 and, for example, a plurality of semiconductor die locations thereon.The distance at which the electrode assembly 8 is desirably positionedfrom the conductive surface of the substrate 14 may depend on theintensity of the fringe electric field generated and on types andconcentrations of electrolytes used in an electrolyte solution 18. Thisdistance may be adjusted to increase or reduce the current densitiesunder the positive electrodes 2 and the negative electrodes 4, whichaffects a plating rate of the metal film. Since the various positive andnegative electrodes may be of different sizes and shapes, lateraldistances between peripheries of adjacent positive electrodes 2 andnegative electrodes 4 as well as transverse, or vertical, distances ofindividual positive electrodes 2 and the negative electrodes 4 away fromthe conductive surface of substrate 14 may also vary. The distancebetween the positive electrodes 2 and negative electrodes 4 of electrodeassembly 8 and the conductive surface of substrate 14 may range fromapproximately 0.1 mm to approximately 1 cm, such as from approximately 2mm to approximately 5 mm. By positioning the electrodes of electrodeassembly 8 closer to the surface of the conductive surface of substrate14, the current density under the electrodes may be increased, whichincreases the plating rate of the metal film under the positiveelectrodes 2. Conversely, by positioning the electrodes of electrodeassembly 8 further from the conductive surface of substrate 14, thecurrent density under the positive electrodes 2 may be decreased todecrease the plating rate of the metal film.

The conductive surface of substrate 14 may be contacted with theelectrolyte solution 18 that includes metal ions of the metal film to bedeposited. These metal ions may electrodeposit on the conductive surfaceof substrate 14 under positive electrodes 2 when the electric field isapplied. The metal ions may dissociate from a metal salt that is solublein a liquid medium of the electrolyte solution 18. The liquid medium maybe aqueous, may include organic solvents, or may include a mixture ofwater and organic solvents. The metal ions may be nickel ions, copperions, cobalt ions, platinum ions, aluminum ions, silver ions, gold ions,chromium ions, iron ions, zinc ions, cadmium ions, palladium ions,platinum ions, tin ions, or bismuth ions. As such, the electrolytesolution 18 may include, but is not limited to, an aqueous solution ofnickel sulfate, nickel chloride, copper sulfate, cobalt chloride, orPt(NH₃)Cl₂. The electrolyte solution 18 may optionally include acids,surfactants, complexing agents, accelerator additives, suppressoradditives, and other conventional ingredients.

To enable the electrolyte solution 18 to flow between the electrodeassembly 8 and the conductive surface of substrate 14, the electrodeassembly 8 does not directly contact the conductive surface of substrate14. The electrolyte solution 18 may be applied to the conductive surfaceof substrate 14 by spraying. Alternatively, the conductive surface ofsubstrate 14 may be immersed in the electrolyte solution 18, such as byimmersing the substrate 14 on chuck or platen 20 in an immersion baththat contains the electrolyte solution 18. When the voltage is appliedto the electrode assembly 8, the fringe electric field 21 is generatedby the alternating polarities of the positive electrodes 2 and thenegative electrodes 4, as shown in FIG. 3. For the sake of clarity, onefringe electric field 21 is illustrated in FIG. 3. However, it isunderstood that multiple fringe electric fields 21 may be presentbetween the alternating positive electrodes 2 and the negativeelectrodes 4. The fringe electric field 21 may desirably be ofsufficient strength to expose the conductive surface of substrate 14 tothe electric field. The voltage may be applied through the electrodeassembly 8 for an amount of time sufficient to deposit a desiredthickness of the metal film on the conductive surface of substrate 14.The metal film may have a thickness ranging from approximately 100 Å toapproximately 5 μm. The fringe electric field 21 may pass through theconductive surface of substrate 14, creating localized, anodic portions22 and cathodic portions 24 on the conductive surface of substrate 14.For instance, a portion of the conductive surface of the substrate 14beneath the positive electrode 2 acts as a cathode (cathodic portion 24)and a portion of the conductive surface of the substrate 14 beneath thenegative electrode 4 acts as an anode (anodic portion 22). The cathodicportion 24 of the conductive surface of substrate 14 has a negativecharge while the anodic portion has a positive charge. For the sake ofclarity and convenience, one cathodic portion 24 and one anodic portion22 are illustrated in FIG. 3. However, it is understood that cathodicportions 24 are formed beneath the plurality of positive electrodes 2and anodic portions are formed beneath the plurality of negativeelectrodes 4.

The metal ions in the electrolyte solution 18 are attracted to theportions of the conductive surface of substrate 14 having an oppositecharge and, therefore, may deposit on the conductive surface ofsubstrate 14 to form the metal film. Since the metal ions in theelectrolytic solution have a positive charge, they are attracted to, andmay deposit on, the cathodic portions 24 of the conductive surface ofsubstrate 14. As shown in FIG. 4, the metal film 26 may be deposited asdiscrete metal features in localized areas of the substrate 14 that arepositioned below the positive electrodes 2. Therefore, the positiveelectrodes 2 may be positioned over portions of the conductive surfaceof substrate 14 that are to be plated with the metal features while thenegative electrodes 4 may be positioned over portions of the conductivesurface of substrate 14 that are to remain unplated. Since the metalions are deposited beneath the positive electrodes 2, the metal featuresmay be selectively plated on the desired portions of the conductivesurface of substrate 14 by adjusting the sizes and configurations ofpositive electrodes 2 and their respective positions over the conductivesurface of substrate 14.

The metal features formed by the noncontact electroplating method of thepresent invention may comprise a film of nickel, copper, cobalt,platinum, aluminum, silver, gold, chromium, iron, zinc, cadmium,palladium, platinum, tin, or bismuth. Metal alloys, such as Sn/Ni, NiWP,CoWP, or Cu/Zn, may also be formed. In one embodiment, the metal film isa film of nickel, copper, cobalt, or platinum. Of course, multiple metallayers may be deposited in superimposition by using the same pattern forelectrode assembly with different electrolyte solutions 18 in differentreservoirs.

By selectively depositing the metal features, the conductive surface ofsubstrate 14 may not include metal film portions extraneous to metalfeatures thereon, which would require subsequent removal. In addition,since the positive electrodes 2 and the negative electrodes 4 are notattached to the conductive surface of substrate 14 by mechanicalelectrical contacts, potential defects in the electrode attachments, aconcern with prior art techniques, cannot occur. Control ofelectroplating the metal features is also enhanced compared toconventional electroless plating techniques. Furthermore, since theelectric field is located adjacent to the portion of the conductivesurface of substrate 14 that is to be plated, the metal features may beuniformly and consistently deposited. The noncontact electroplatingmethod may also enable the selective deposition of the metal featureswithout using a mask. Since the metal features are depositedselectively, a mask is not required to cover portions of the conductivesurface of substrate 14 that are to remain unplated. Instead, afterplating is completed, unplated portions of the seed layer comprising theconductive surface may be easily removed by a selective solvent. Thesolvent may be chosen by one of ordinary skill in the art based on thematerials used in the seed layer and in the substrate 14.

As described above, in one embodiment, the electrode assembly 8 isattached to a DC power supply to selectively deposit the metal featureson the conductive surface of substrate 14. In another embodiment, themetal features are deposited over areas of the conductive surface ofsubstrate 14 proximate and beneath each electrode 2 and 4 by attachingthe electrodes 2 and 4 of electrode assembly 8 to an AC power supply. Inthis situation, wherein power supply 10 comprises an AC power supplyoperably coupled to electrodes 2 and 4 in the same manner as the DCpower supply previously described with respect to FIG. 1, the polarityof electrodes 2 and 4 varies and metal features may be deposited underboth electrodes 2 and electrodes 4 because the polarities of theelectrodes reverse with each cycle of the AC power supply. For instance,during one cycle of the AC power supply, the electrodes 2 may exhibit apositive polarity while the electrodes 4 may exhibit a negativepolarity. However, during a second, reverse AC power cycle, thepolarities of the electrodes are reversed. Due to the cycling of the ACpower supply, portions of the conductive surface of substrate 14 underthe electrodes 2 or under the electrodes 4 may be negatively charged andcomprise a cathodic portion 24. In other words, at different points intime, portions of the conductive surface of substrate 14 beneath theelectrodes 2 or beneath the electrodes 4 have a negative charge uponwhich the metal ions from electrolyte solution 18 may deposit to formthe metal features. Accordingly, an AC power supply may be used to platemetal features in closer proximity (smaller spacing or pitch) on theconductive surface of substrate 14 that is positioned beneath theelectrode assembly 8 than if a DC power supply is employed. Using thepresent invention may enable the metal features to be deposited moreuniformly over larger portions of the conductive surface of substrate 14than with prior art techniques employing electrode edge connections at awafer periphery, which result in a drop in potential toward the wafercenter. The noncontact electroplating process of the present inventionmay be used to form metal features on the conductive surface ofsubstrate 14 including, but not limited to, bond pads, traces anddamascene structures. Electroplating such metal features is one of manysteps in fabricating the integrated circuits. As such, theelectroplating process of the present invention may be used to formintermediate semiconductor device structures. By using the noncontactelectroplating process of the present invention, the bond pads may beselectively formed on the conductive surface of substrate 14 withoutundesirably plating the metal film 26 on other portions of the substrate14. The noncontact electroplating process may also be used to form metalinterconnects of the damascene structures. By selectively plating themetal interconnects, subsequent polishing steps to remove extraneousfilm may be reduced or eliminated. The fabrication of the damascenestructures is known in the art and, therefore, is not discussed indetail herein.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

1. A method of electroplating a semiconductor substrate, comprising:providing an electrode assembly comprising a plurality of adjacent,mutually spaced and electrically isolated electrodes connected in seriesso as to be oppositely polarized when a voltage is applied thereacross;positioning the electrode assembly over a conductive surface of asubstrate; applying an electrolyte solution to the conductive surface ofthe substrate; applying a voltage to the plurality of electrodes; andforming discrete metal features on portions of the conductive surface ofthe substrate positioned beneath the electrodes of the pluralityexhibiting a positive polarity.
 2. The method of claim 1, furthercomprising disposing an insulating material between each of theplurality of adjacent electrodes.
 3. The method of claim 1, whereinpositioning the electrode assembly over the conductive surface of thesubstrate comprises positioning the electrodes of the plurality in closeproximity to the conductive surface of the substrate without theelectrodes of the plurality contacting the conductive surface of thesubstrate.
 4. The method of claim 1, wherein positioning the electrodeassembly over the conductive surface of the substrate comprisespositioning the electrodes of the plurality exhibiting the positivepolarity over portions of the conductive surface of the substrate uponwhich the metal features are to be formed.
 5. The method of claim 1,wherein positioning the electrode assembly over the conductive surfaceof the substrate comprises positioning the electrodes of the pluralityexhibiting negative polarity over portions of the conductive surface ofthe substrate that are to remain unplated.
 6. The method of claim 1,wherein positioning the electrode assembly over the conductive surfaceof the substrate comprises positioning the electrodes of the pluralityfrom approximately 0.1 mm to approximately 1 cm away from the conductivesurface of the substrate.
 7. The method of claim 1, wherein positioningthe electrode assembly over the conductive surface of the substratecomprises positioning the electrodes of the plurality from approximately2 mm to approximately 5 mm away from the conductive surface of thesubstrate.
 8. The method of claim 1, wherein applying the electrolytesolution to the conductive surface of the substrate comprises applyingthe electrolyte solution comprising metal ions selected from the groupconsisting of nickel ions, copper ions, cobalt ions, platinum ions,aluminum ions, silver ions, gold ions, chromium ions, iron ions, zincions, cadmium ions, palladium ions, platinum ions, tin ions, and bismuthions.
 9. The method of claim 1, wherein applying the electrolytesolution to the conductive surface of the substrate comprises applyingthe electrolyte solution selected from the group consisting of nickelsulfate, nickel chloride, copper sulfate, cobalt chloride, andPt(NH₃)Cl₂.
 10. The method of claim 1, wherein applying the voltage tothe plurality of electrodes comprises generating a fringe electricalfield of a magnitude to pass through the conductive surface of thesubstrate.
 11. The method of claim 1, wherein applying the voltage tothe plurality of electrodes comprises connecting the plurality ofelectrodes to a DC power supply.
 12. The method of claim 1, whereinapplying the voltage to the plurality of electrodes comprises connectingthe plurality of electrodes to an AC power supply.
 13. The method ofclaim 1, wherein applying the voltage to the plurality of electrodescomprises forming cathodic portions on the conductive surface of thesubstrate beneath the electrodes of the plurality exhibiting thepositive polarity and forming anodic portions on the conductive surfaceof the substrate beneath the electrodes of the plurality exhibiting anegative polarity.
 14. The method of claim 1, wherein forming the metalfeatures on portions of the conductive surface of the substratepositioned beneath the electrodes of the plurality exhibiting thepositive polarity comprises selectively depositing the metal features oncathodic portions of the conductive surface of the substrate.
 15. Themethod of claim 14, wherein selectively depositing the metal features onthe cathodic portions of the conductive surface of the substratecomprises operably coupling the plurality of electrodes to a DC powersupply.
 16. The method of claim 1, wherein forming the metal features onportions of the conductive surface of the substrate positioned beneaththe electrodes of the plurality exhibiting a positive polarity comprisesforming the metal features on the conductive surface of the substratebeneath each electrode of the plurality.
 17. The method of claim 16,wherein forming the metal features on the conductive surface of thesubstrate comprises operably coupling the plurality of electrodes to anAC power supply.
 18. The method of claim 1, wherein forming the metalfeatures on portions of the conductive surface of the substratepositioned beneath the electrodes of the plurality exhibiting a positivepolarity comprises forming the metal features from at least one ofnickel, copper, cobalt, platinum, aluminum, silver, gold, chromium,iron, zinc, cadmium, palladium, platinum, tin, and bismuth.
 19. Themethod of claim 1, wherein forming the metal features on portions of theconductive surface of the substrate positioned beneath the electrodes ofthe plurality exhibiting a positive polarity comprises forming the metalfeatures from at least one of nickel, copper, cobalt, and platinum. 20.An electroplating system, comprising: an electrode assembly comprising aplurality of adjacent, mutually spaced and electrically isolatedelectrodes connected in series so as to be oppositely polarized when avoltage is applied thereacross; a power supply operably coupled to theplurality of electrodes; a platen for bearing a substrate on which metalfeatures are to be formed; and an electrode support configured forsuspending the electrode assembly over an upper surface of the substratedisposed on the platen in spaced relation to and in alignment with thesubstrate.
 21. The electroplating system of claim 20, further comprisinga dielectric material disposed between adjacent electrodes of theplurality.
 22. The electroplating system of claim 20, wherein theplurality of electrodes is configured and spaced to produce a fringeelectric field between adjacent, oppositely polarized electrodes when avoltage from the power supply is applied thereto.
 23. The electroplatingsystem of claim 20, wherein each electrode of the plurality ofelectrodes is formed from graphite, gold, or platinum.
 24. Theelectroplating system of claim 20, wherein the power supply is an ACpower supply.
 25. The electroplating system of claim 20, wherein thepower supply is a DC power supply.
 26. The electroplating system ofclaim 20, wherein each of the plurality of electrodes exhibiting apositive polarity when the voltage is applied is sized, configured andlocated to define a pattern that corresponds to a pattern of the metalfeatures to be plated on the substrate.
 27. The electroplating system ofclaim 20, wherein the electrode support is configured to position theelectrodes of the plurality from approximately 0.1 mm to approximately 1cm away from the upper surface of the substrate when the substrate isdisposed on the platen.
 28. The electroplating system of claim 20,wherein the electrode support is configured to position the electrodesof the plurality from approximately 2 mm to approximately 5 mm away fromthe upper surface of the substrate when the substrate is disposed on theplaten.
 29. A method of selectively depositing metal features on asurface of a semiconductor substrate, comprising: providing asemiconductor substrate having a conductive surface thereon; andnegatively charging selective portions of the conductive surface in asize, shape and location of metal features to be formed thereon in thepresence of an electrolyte solution containing ions of a metal for themetal features.
 30. The method of claim 29, further comprising formingthe conductive surface as a conductive seed layer.
 31. The method ofclaim 29, further comprising negatively charging the selective portionsof the conductive surface by exposing the conductive surface to a fringeelectrical field generated above and in proximity to, but out of contactwith, the conductive surface.
 32. The method of claim 31, furthercomprising generating the fringe electrical field between a plurality oflaterally adjacent, mutually spaced and oppositely polarized electrodesdisposed above the conductive surface.
 33. The method of claim 32,further comprising forming the metal features under alternatingelectrodes of the plurality.
 34. The method of claim 33, wherein formingthe metal features under alternating electrodes further comprisesconnecting the alternating electrodes in series and applying a DCvoltage thereacross.
 35. The method of claim 32, further comprisingforming the metal features under adjacent electrodes of the plurality.36. The method of claim 35, wherein forming the metal features underadjacent electrodes of the plurality further comprises connecting theadjacent electrodes in series and applying an AC voltage thereacross.